Methods and apparatus for efficient complex long multiplication and covariance matrix implementation

ABSTRACT

Efficient computation of complex long multiplication results and an efficient calculation of a covariance matrix are described. A parallel array VLIW digital signal processor is employed along with specialized complex long multiplication instructions and communication operations between the processing elements which are overlapped with computation to provide very high performance operation. Successive iterations of a loop of tightly packed VLIWs may be used allowing the complex multiplication pipeline hardware to be efficiently used.

RELATED APPLICATIONS

The present application is a continuation of U.S. Ser. No. 11/438,418filed May 22, 2006, now U.S. Pat. No. 7,680,873, which is a continuationof U.S. Ser. No. 10/004,010 filed Nov. 1, 2001, now U.S. Pat. No.7,072,929 and claims the benefit of U.S. Provisional Application Ser.No. 60/244,861 filed Nov. 1, 2000, which are incorporated by referenceherein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to improvements to parallelprocessing, and more particularly to methods and apparatus forefficiently calculating the result of a long complex multiplication.Additionally, the present invention relates to the advantageous use ofthis approach for the calculation of a covariance matrix.

BACKGROUND OF THE INVENTION

The product of two complex numbers x and y is defined to bez=x_(R)y_(R)−x₁y₁+i(x_(R)y₁+x₁y_(R)), where x=x_(R)+ix₁, y=y_(R)+iy₁ andi is an imaginary number, or the square root of negative one, withi²=−1. This complex multiplication of x and y is calculated in a varietyof contexts, and it has been recognized that it will be highlyadvantageous to perform this calculation faster and more efficiently.

SUMMARY OF THE INVENTION

The present invention defines hardware instructions to calculate theproduct of two complex numbers encoded as a pair of two fixed-pointnumbers of 16 bits each. The product may be calculated in two cycleswith single cycle pipeline throughput efficiency, or in a single cycle.The product is encoded as a 32 bit real component and a 32 bit imaginarycomponent. The present invention also defines a series of multiplycomplex instructions with an accumulate operation. Additionally, thepresent invention also defines a series of multiply complex instructionswith an extended precision accumulate operation. The complex longinstructions and methods of the present invention may be advantageouslyused in a variety of contexts, including calculation of a fast Fouriertransform as addressed in U.S. patent application Ser. No. 09/337,839filed Jun. 22, 1999 entitled “Efficient Complex Multiplication and FastFourier Transform (FFT) Implementation on the ManArray Architecture”which is incorporated by reference herein in its entirety. The multiplycomplex instructions of the present invention may be advantageously usedin the computation of a covariance matrix, as described below.

A more complete understanding of the present invention, as well as otherfeatures and advantages of the invention will be apparent from thefollowing Detailed Description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary 2×2 ManArray iVLIW processor;

FIG. 2A illustrates a multiply complex long (MPYCXL) instruction inaccordance with the present invention;

FIGS. 2B and 2C illustrate the syntax and operation of the MPYCXLinstruction of FIG. 2A;

FIG. 3A illustrates a multiply complex conjugate long (MPYCXJL)instruction in accordance with the present invention;

FIGS. 3B and 3C illustrate the syntax and operation of the MPYCXJLinstruction of FIG. 3A;

FIG. 4A illustrates a multiply complex long accumulate (MPYCXLA)instruction in accordance with the present invention;

FIGS. 4B and 4C illustrate the syntax and operation of the MPYCXLAinstruction of FIG. 4A;

FIG. 5A illustrates a multiply complex conjugate long accumulate(MPYCXJLA) instruction in accordance with the present invention;

FIGS. 5B and 5C illustrate the syntax and operation of the MPYCXJLAinstruction of FIG. 5A;

FIG. 6A illustrates a multiply complex long extended precisionaccumulate (MPYCXLXA) instruction in accordance with the presentinvention;

FIGS. 6B and 6C illustrate the syntax and operation of the MPYCXLXAinstruction of FIG. 6A;

FIG. 7A illustrates a multiply complex conjugate long extended precisionaccumulate (MPYCXJLXA) instruction in accordance with the presentinvention;

FIGS. 7B and 7C illustrates the syntax and operation of the MPYCXJLXAinstruction of FIG. 7A;

FIG. 8 shows a block diagram illustrating various aspects of hardwaresuitable for performing the MPYCXL, MPYCXJL, MPYCXLA, MPYCXJLA,MPYCXJLA, MPYCXLXA and MPYCXJLXA instructions in two cycles of operationin accordance with the present invention;

FIG. 9 shows an integrated product adder and accumulator in accordancewith the present invention;

FIG. 10 shows a block diagram illustrating various aspects of hardwaresuitable for performing the MPYCXL, MPYCXJL, MPYCXLA, MPYCXJLA,MPYCXJLA, MPYCXLXA and MPYCXJLXA instructions in a single cycle ofoperation in accordance with the present invention; and

FIGS. 11A-11I illustrate the calculation of a covariance matrix on a 2×2processing array in accordance with the present invention.

DETAILED DESCRIPTION

Further details of a presently preferred ManArray core, architecture,and instructions for use in conjunction with the present invention arefound in: U.S. patent application Ser. No. 08/885,310 filed Jun. 30,1997, now U.S. Pat. No. 6,023,753, U.S. patent application Ser. No.08/949,122 filed Oct. 10, 1997, now U.S. Pat. No. 6,167,502, U.S. patentapplication Ser. No. 09/169,256 filed Oct. 9, 1998, now U.S. Pat. No.6,167,501, U.S. patent application Ser. No. 09/169,072 filed Oct. 9,1998, now U.S. Pat. No. 6,219,776, U.S. patent application Ser. No.09/187,539 filed Nov. 6, 1998, now U.S. Pat. No. 6,151,668, U.S. patentapplication Ser. No. 09/205,558 filed Dec. 4, 1998, now U.S. Pat. No.6,173,389, U.S. patent application Ser. No. 09/215,081 filed Dec. 18,1998, now U.S. Pat. No. 6,101,592, U.S. patent application Ser. No.09/228,374 filed Jan. 12, 1999, now U.S. Pat. No. 6,216,223, U.S. patentapplication Ser. No. 09/471,217 filed Dec. 23, 1999, now U.S. Pat. No.6,260,082, U.S. patent application Ser. No. 09/472,372 filed Dec. 23,1999, now U.S. Pat. No. 6,256,683, U.S. patent application Ser. No.09/238,446 filed Jan. 28, 1999, U.S. patent application Ser. No.09/267,570 filed Mar. 12, 1999, U.S. patent application Ser. No.09/337,839 filed Jun. 22, 1999, U.S. patent application Ser. No.09/350,191 filed Jul. 9, 1999, U.S. patent application Ser. No.09/422,015 filed Oct. 21, 1999, U.S. patent application Ser. No.09/432,705 filed Nov. 2, 1999, U.S. patent application Ser. No.09/596,103 filed Jun. 16, 2000, U.S. patent application Ser. No.09/598,567 filed Jun. 21, 2000, U.S. patent application Ser. No.09/598,564 filed Jun. 21, 2000, U.S. patent application Ser. No.09/598,566 filed Jun. 21, 2000, U.S. patent application Ser. No.09/598,558 filed Jun. 21, 2000, U.S. patent application Ser. No.09/598,084 filed Jun. 21, 2000, U.S. patent application Ser. No.09/599,980 filed Jun. 22, 2000, U.S. patent application Ser. No.09/711,218 filed Nov. 9, 2000, U.S. patent application Ser. No.09/747,056 filed Dec. 12, 2000, U.S. patent application Ser. No.09/853,989 filed May 11, 2001, U.S. patent application Ser. No.09/886,855 filed Jun. 21, 2001, U.S. patent application Ser. No.09/791,940 filed Feb. 23, 2001, U.S. patent application Ser. No.09/792,819 filed Feb. 23, 2001, U.S. patent application Ser. No.09/791,256 filed Feb. 23, 2001, U.S. patent application Ser. No.10/013,908 entitled “Methods and Apparatus for Efficient VocoderImplementations” filed Oct. 19, 2001, Provisional Application Ser. No.60/251,072 filed Dec. 4, 2000, Provisional Application Ser. No.60/281,523 filed Apr. 4, 2001, Provisional Application Ser. No.60/283,582 filed Apr. 13, 2001, Provisional Application Ser. No.60/287,270 filed Apr. 27, 2001, Provisional Application Ser. No.60/288,965 filed May 4, 2001, Provisional Application Ser. No.60/298,624 filed Jun. 15, 2001, Provisional Application Ser. No.60/298,695 filed Jun. 15, 2001, Provisional Application Ser. No.60/298,696 filed Jun. 15, 2001, Provisional Application Ser. No.60/318,745 filed Sep. 11, 2001, Provisional Application Ser. No.60/340,620 entitled “Methods and Apparatus for Video Coding” filed Oct.30, 2001, Provisional Application Ser. No. 60/335,159 entitled “Methodsand Apparatus for a Bit Rate Instruction” filed Nov. 1, 2001, all ofwhich are assigned to the assignee of the present invention andincorporated by reference herein in their entirety.

In a presently preferred embodiment of the present invention, a ManArray2×2 iVLIW single instruction multiple data stream (SIMD) processor 100shown in FIG. 1 contains a controller sequence processor (SP) combinedwith processing element-0 (PE0) SP/PE0 101, as described in furtherdetail in U.S. application Ser. No. 09/169,072 entitled “Methods andApparatus for Dynamically Merging an Array Controller with an ArrayProcessing Element”. Three additional PEs 151, 153, and 155 are alsoutilized. It is noted that the PEs can be also labeled with their matrixpositions as shown in parentheses for PE0 (PE00) 101, PE1 (PE01) 151,PE2 (PE10) 153, and PE3 (PE11) 155.

The SP/PE0 101 contains a fetch controller 103 to allow the fetching ofshort instruction words (SIWs) from a 32-bit instruction memory 105. Thefetch controller 103 provides the typical functions needed in aprogrammable processor such as a program counter (PC), branchcapability, digital signal processing, EP loop operations, support forinterrupts, and also provides the instruction memory management controlwhich could include an instruction cache if needed by an application. Inaddition, the SIW I-Fetch controller 103 dispatches 32-bit SIWs to theother PEs in the system by means of a 32-bit instruction bus 102.

In this exemplary system, common elements are used throughout tosimplify the explanation, though actual implementations are not solimited. For example, the execution units 131 in the combined SP/PE0 101can be separated into a set of execution units optimized for the controlfunction, e.g. fixed point execution units, and the PE0 as well as theother PEs 151, 153 and 155 can be optimized for a floating pointapplication. For the purposes of this description, it is assumed thatthe execution units 131 are of the same type in the SP/PE0 and the otherPEs. In a similar manner, SP/PE0 and the other PEs use a fiveinstruction slot iVLIW architecture which contains a very longinstruction word memory (VIM) memory 109 and an instruction decode andVIM controller function unit 107 which receives instructions asdispatched from the SP/PE0's I-Fetch unit 103 and generates the VIMaddresses-and-control signals 108 required to access the iVLIWs storedin the VIM. These iVLIWs are identified by the letters SLAMD in VIM 109.The loading of the iVLIWs is described in further detail in U.S. patentapplication Ser. No. 09/187,539 entitled “Methods and Apparatus forEfficient Synchronous MIMD Operations with iVLIW PE-to-PECommunication”. Also contained in the SP/PE0 and the other PEs is acommon PE configurable register file 127 which is described in furtherdetail in U.S. patent application Ser. No. 09/169,255 entitled “Methodsand Apparatus for Dynamic Instruction Controlled ReconfigurationRegister File with Extended Precision”.

Due to the combined nature of the SP/PE0, the data memory interfacecontroller 125 must handle the data processing needs of both the SPcontroller, with SP data in memory 121, and PE0, with PE0 data in memory123. The SP/PE0 controller 125 also is the source of the data that issent over the 32-bit broadcast data bus 126. The other PEs 151, 153, and155 contain common physical data memory units 123′, 123″, and 123′″though the data stored in them is generally different as required by thelocal processing done on each PE. The interface to these PE datamemories is also a common design in PEs 1, 2, and 3 and indicated by PElocal memory and data bus interface logic 157, 157′ and 157″.Interconnecting the PEs for data transfer communications is the clusterswitch 171 more completely described in U.S. patent application Ser. No.08/885,310 entitled “Manifold Array Processor”, U.S. application Ser.No. 09/949,122 entitled “Methods and Apparatus for Manifold ArrayProcessing”, and U.S. application Ser. No. 09/169,256 entitled “Methodsand Apparatus for ManArray PE-to-PE Switch Control”. The interface to ahost processor, other peripheral devices, and/or external memory can bedone in many ways. The primary mechanism shown for completeness iscontained in a direct memory access (DMA) control unit 181 that providesa scalable ManArray data bus 183 that connects to devices and interfaceunits external to the ManArray core. The DMA control unit 181 providesthe data flow and bus arbitration mechanisms needed for these externaldevices to interface to the ManArray core memories via the multiplexedbus interface represented by line 185. A high level view of a ManArrayControl Bus (MCB) 191 is also shown.

All of the above noted patents are assigned to the assignee of thepresent invention and incorporated herein by reference in theirentirety.

Turning now to specific details of the ManArray processor as adapted bythe present invention, the present invention defines the followingspecial hardware instructions that execute in each multiply accumulateunit (MAU), one of the execution units 131 of FIG. 1 and in each PE, tohandle the multiplication of complex numbers.

FIG. 2A shows a multiply complex long (MPYCXL) instruction 200 for themultiplication of two complex numbers in accordance with the presentinvention. The syntax and operation description 210 of the MPYCXLinstruction 200 are shown in FIGS. 2B and 2C. As seen in diagram 220 ofFIG. 2C, the MPYCXL instruction 200 provides for the multiplication oftwo complex numbers stored in source register Rx and source register Ry.In step 222, the complex numbers to be multiplied are organized in thesource registers such that H1 contains the real component of the complexnumbers and H0 contains the imaginary component of the complex numbers.In step 224, the complex numbers are multiplied to produce the productsXr*Yr, Xr*Yi, Xi*Yr and Xi*Yi. Next, in step 226, the products aresubtracted and added in the form of (Xr*Yr)−(Xi*Yi) and (Xr*Yi)+(Xi*Yr).In step 228, the final result is written back to the target registers atthe end of an operation cycle of the MPYCXL instruction 200 with a32-bit real component and a 32-bit imaginary component placed in thetarget registers such that Rto contains the 32-bit real component andRte contains the 32-bit imaginary component.

FIG. 3A shows a multiply complex conjugate long (MPYCXJL) instruction300 for the multiplication of a first complex number and the conjugateof a second complex number in accordance with the present invention. Thesyntax and operation description 310 of the MPYCXJL instruction 300 areshown in FIGS. 3B and 3C. As seen in diagram 320 of FIG. 3C, the MPYCXJLinstruction 300 provides for the multiplication of two complex numbersstored in source register Rx and source register Ry. In step 322, thecomplex numbers to be multiplied are organized in the source registerssuch that H1 contains the real component of the complex numbers and H0contains the imaginary component of the complex numbers. In step 324,the complex numbers are multiplied to produce the products Xr*Yr, Xr*Yi,Xi*Yr and Xi*Yi. Next, in step 326, the products are subtracted andadded in the form of (Xr*Yr)+(Xi*Yi) and (Xi*Yr)−(Xr*Yi). In step 328,the final result is written back to the target registers at the end ofan operation cycle of the MPYCXJL instruction 300 with a 32-bit realcomponent and a 32-bit imaginary component placed in the targetregisters such that Rto contains the 32-bit real component and Rtecontains the 32-bit imaginary component.

FIG. 4A shows a multiply complex long accumulate (MPYCXLA) instruction400 for the multiplication of two complex numbers to form a productwhich is accumulated with the contents of target registers in accordancewith the present invention. The syntax and operation description 410 ofthe MPYCXLA instruction 400 are shown in FIGS. 4B and 4C. As seen indiagram 420 of FIG. 4C, the MPYCXLA instruction 400 provides for themultiplication of two complex numbers stored in source register Rx andsource register Ry. In step 422, the complex numbers to be multipliedare organized in the source registers such that H1 contains the realcomponent of the complex numbers and H0 contains the imaginary componentof the complex numbers. In step 424, the complex numbers are multipliedto produce the products Xr*Yr, Xr*Yi, Xi*Yr and Xi*Yi. Next, in step426, the products are subtracted and added in the form of(Xr*Yr)−(Xi*Yi) and (Xr*Yi)+(Xi*Yr). In step 428, (Xr*Yr)−(Xi*Yi) isadded to the contents of target register Rto and (Xr*Yi)+(Xi*Yr) isadded, or accumulated, to the contents of target register Rte. The finalresult is written back to the target registers at the end of anoperation cycle of the MPYCXLA instruction 400 with a 32-bit realcomponent and a 32-bit imaginary component placed in the targetregisters such that Rto contains the 32-bit real component and Rtecontains the 32-bit imaginary component. For a two cycle embodiment, thetarget registers are fetched on a second cycle of execution to allowrepetitive pipelining to a single accumulation register even-odd pair.

FIG. 5A shows a multiply complex conjugate long accumulate (MPYCXJLA)instruction 500 for the multiplication of a first complex number and theconjugate of a second complex number to form a product which isaccumulated with the contents of target registers in accordance with thepresent invention. The syntax and operation description 510 of theMPYCXJLA instruction 500 are shown in FIGS. 5B and 5C. As seen indiagram 520 of FIG. 5C, the MPYCXJLA instruction 500 provides for themultiplication of two complex numbers stored in source register Rx andsource register Ry. In step 522, the complex numbers to be multipliedare organized in the source registers such that H1 contains the realcomponent of the complex numbers and H0 contains the imaginary componentof the complex numbers. In step 524, the complex numbers are multipliedto produce the products Xr*Yr, Xr*Yi, Xi*Yr and Xi*Yi. Next, in step526, the products are added and subtracted in the form of(Xr*Yr)+(Xi*Yi) and (Xi*Yr)−(Xr*Yi). In step 528, (Xr*Yr)+(Xi*Yi) isadded, or accumulated, to the contents of target register Rto and(Xi*Yr)−(Xr*Yi) is added to the contents of target register Rte. Thefinal result is written back to the target registers at the end of anoperation cycle of the MPYCXJLA instruction 500 with a 32-bit realcomponent and a 32-bit imaginary component placed in the targetregisters such that Rto contains the 32-bit real component and Rtecontains the 32-bit imaginary component. For a two cycle embodiment, thetarget registers are fetched on the second cycle of execution to allowrepetitive pipelining to a single accumulation register even-odd pair.

FIG. 6A shows a multiply complex long extended precision accumulate(MPYCXLXA) instruction 600 for the multiplication of two complex numbersto form a product which is accumulated with the contents of the extendedprecision target registers in accordance with the present invention. Thesyntax and operation description 610 of the MPYCXLXA instruction 600 areshown in FIGS. 6B and 6C. As seen in diagram 620 of FIG. 6C, theMPYCXLXA instruction 600 provides for the multiplication of two complexnumbers stored in source register Rx and source register Ry. In step622, the complex numbers to be multiplied are organized in the sourceregisters such that H1 contains the real component of the complexnumbers and H0 contains the imaginary component of the complex numbers.In step 624, the complex numbers are multiplied to produce the productsXr*Yr, Xr*Yi, Xi*Yr and Xi*Yi. Next, in step 626, the products aresubtracted and added in the form of (Xr*Yr)−(Xi*Yi) and (Xr*Yi)+(Xi*Yr).In step 628, the 32-bit value (Xr*Yr)−(Xi*Yi) is added to the contentsof the extended precision target register XPRBo∥Rto and the 32-bit value(Xr*Yi)+(Xi*Yr) is added to the contents of the extended precisiontarget register XPRBe∥Rte. The final result is written back to theextended precision target registers at the end of an operation cycle ofthe MPYCXLXA instruction 600 with a 40-bit real component and a 40-bitimaginary component placed in the target registers such that XPRBo∥Rtocontains the 40-bit real component and XPRBe∥Rte contains the 40-bitimaginary component. For a two cycle embodiment, the target registersare fetched on the second cycle of execution to allow repetitivepipelining to a single accumulation register even-odd pair.

The extended precision bits for the 40-bit results are provided by theextended precision register (XPR). The specific sub-registers used in anextended precision operation depend on the size of the accumulation(dual 40-bit or single 80-bit) and on the target CRF register pairspecified in the instruction. For dual 40-bit accumulation, the 8-bitextension registers XPR.B0 and XPR.B1 (or XPR.B2 and XPR.B3) areassociated with a pair of CRF registers. For single 80-bit accumulation,the 16-bit extension register XPR.H0 (or XPR.H1) is associated with apair of CRF registers. During the dual 40-bit accumulation, the eventarget register is extended using XPR.B0 or XPR.B2, and the odd targetregister is extended using XPR.B1 or XPR.B3. The tables 602, 604, 608,612 and 614 of FIG. 6A illustrate the register usage in detail.

As shown in FIG. 6A, the XPR byte that is used depends on the Rte.Further details of an XPR register suitable for use with the presentinvention are provided in U.S. patent application Ser. No. 09/599,980entitled “Methods and Apparatus for Parallel Processing Utilizing aManifold Array (ManArray) Architecture and Instruction Syntax” filed onJun. 20, 2000 which is incorporated by reference herein in its entirety.

FIG. 7A shows a multiply complex conjugate long extended precisionaccumulate (MPYCXJLXA) instruction 700 for the multiplication of a firstcomplex number and the conjugate of a second complex number to form aproduct which is accumulated with the contents of the extended precisiontarget registers in accordance with the present invention. The syntaxand operation description 710 of the MPYCXJLXA instruction 700 are shownin FIGS. 7B and 7C. As seen in diagram 720 of FIG. 7C, the MPYCXJLXAinstruction 700 provides for the multiplication of two complex numbersstored in source register Rx and source register Ry. In step 722, thecomplex numbers to be multiplied are organized in the source registerssuch that H1 contains the real component of the complex numbers and H0contains the imaginary component of the complex numbers. In step 724,the complex numbers are multiplied to produce the products Xr*Yr, Xr*Yi,Xi*Yr and Xi*Yi. Next, in step 726, the products are subtracted andadded in the form of (Xr*Yr)+(Xi*Yi) and (Xi*Yr)−(Xr*Yi). In step 728,the 32-bit value (Xr*Yr)+(Xi*Yi) is added to the contents of theextended precision target register XPRBe∥Rte and the 32-bit value(Xi*Yr)−(Xr*Yi) is added to the contents of the extended precisiontarget register XPRBo∥Rto. The final result is written back to theextended precision target registers at the end of an operation cycle ofthe MPYCXJLXA instruction 700 with a 40-bit real component and a 40-bitimaginary component placed in the target registers such that XPRBo∥Rtocontains the 40-bit real component and XPRBe∥Rte contains the 40-bitimaginary component. For a two cycle embodiment, the target registersare fetched on the second cycle of execution to allow repetitivepipelining to a single accumulation register even-odd pair.

The extended precision bits for the 40-bit results are provided by theextended precision register (XPR). The specific sub-registers used in anextended precision operation depend on the size of the accumulation(dual 40-bit or single 80-bit) and on the target CRF register pairspecified in the instruction. For dual 40-bit accumulation, the 8-bitextension registers XPR.B0 and XPR.B1 (or XPR.B2 and XPR.B3) areassociated with a pair of CRF registers. For single 80-bit accumulation,the 16-bit extension register XPR.H0 (or XPR.H1) is associated with apair of CRF registers. During the dual 40-bit accumulation, the eventarget register is extended using to XPR.B0 or XPR.B2, and the oddtarget register is extended using XPR.B1 or XPR.B3. The tables 702, 704,708, 712 and 714 of FIG. 7A illustrate the register usage in detail. Asshown in FIG. 7A, the XPR byte that is used depends on the Rte.

All of the above instructions 200, 300, 400, 500, 600 and 700 maycomplete in 2 cycles and are pipelineable. That is, another operationcan start executing on the execution unit after the first cycle. Inaccordance with another aspect of the present invention, all of theabove instructions 200, 300, 400, 500, 600 and 700 may complete in asingle cycle.

FIG. 8 shows a high level view of a hardware apparatus 800 suitable forimplementing the multiply complex instructions for execution in twocycles of operation. This hardware capability may be advantageouslyembedded in the ManArray multiply accumulate unit (MAU), one of theexecution units 131 of FIG. 1 and in each PE, along with other hardwarecapability supporting other MAU instructions. As a pipelined operation,the first execute cycle begins with a read of source register operandsRy.H1, Ry.H0, Rx.H1 and Rx.H0 from the compute register file (CRF) shownas registers 803 and 805 in FIG. 8 and as registers 111, 127, 127′,127″, and 127′″ in FIG. 1. These operands may be viewed as correspondingto the operands Yr, Yi, Xr and Xi described above. The operand valuesare input to multipliers 807, 809, 811 and 813 after passing throughmultiplexer 815 which aligns the halfword operands.

Multipliers 807 and 809 are used as 16×16 multipliers for these complexmultiplications. The 32×16 notation indicates these two multipliers arealso used to support 32×32 multiplies for other instructions in theinstruction set architecture (ISA). Multiplexer 815 is controlled by aninput control signal 817. The outputs of the multipliers, Xr*Yr, Xr*Yi,Xi*Yr and Xi*Yi, are input to registers 824 a, 824 b, 824 c and 824 dafter passing through multiplexer 823 which aligns the outputs based onthe type of multiplication operation. The registers 824 a, 824 b, 824 cand 824 d latch the multiplier outputs, allowing pipelined operation ofa second instruction to begin. An output control signal 825 controls therouting of the multiplier outputs to the input registers 824 a, b, c, dof adders 819 and 821. The second execute cycle, which can occur while anew multiply complex instruction is using the first cycle executefacilities, begins with adders 819 and 821 operating on the contents ofregisters 824 a, 824 b, 824 c and 824 d. The adders 819 and 821 functionas either adders or subtractors based on a conjugate select signal 827,which is set depending on the type of complex multiplication beingexecuted.

The outputs of the adders 819 and 821 are then passed to accumulators833 and 835. If an accumulate operation is not being performed, a zerovalue is output from multiplexers 829 and 831 to accumulators 833 and835 to produce a zero input for no accumulation. If an accumulateoperation is being performed, the contents of current target registersRt.H1 and Rt.H1, shown as registers 837 and 839, is output frommultiplexers 829 and 831 to accumulators 833 and 835 as an input toproduce an accumulated result. Multiplexers 829 and 831 are controlledby an accumulator control signal 841. The outputs of the accumulators823 and 825 are then written to the target registers 837 and 839 whichcontain the 32 bit real result and the 32 bit imaginary result,respectively.

If an extended precision operation is being performed, the accumulationis augmented eight extra bits by adding the contents of an extendedprecision registers 843 and 844 to the sign extended output of adders819 and 821. The outputs of the accumulators 833 and 835 are thenwritten back to the target registers 837 and 839, and the XPR registers843 and 844, such that registers 843 and 837 contain one of the 40 bitresults and registers 844 and 839 contain the other 40 bit result. Realand imaginary results are specified by instructions.

FIG. 9 shows an integrated product adder and accumulator (IPAA) 900 inaccordance with the present invention. IPAA 900 may be suitably utilizedwith hardware 800, replacing an adder and accumulator, to decrease delayand improve performance. For instructions not requiring an accumulatedresult, select signal 902 controls multiplexer 904 to input a zero value910 to IPAA 900 which performs addition or subtraction on productoperands 906 and 908. For instructions requiring an accumulated result,select signal 902 controls multiplexer 904 to input an accumulated input912 to IPAA 900 which performs addition or subtraction on productoperands 906 and 908 to produce an accumulated result.

FIG. 10 shows a high level view of a hardware apparatus 800′ suitablefor implementing the multiply complex instructions for execution in asingle cycle of operation. Hardware apparatus 800′ includes many of thesame elements as hardware apparatus 800, with common elements to bothembodiments designated by the same element numbers. The multiplieralignment multiplexer 823 and registers 824 a, 824 b, 824 c and 824 d ofapparatus 800 are replaced by a logical array 850, allowing the multiplycomplex instructions to complete in a single cycle of operation. Thelogical array 850 properly aligns the outputs of multipliers 807, 809,811 and 813 for transmission to the adders 819 and 821.

Computation of a Covariance Matrix

The multiply complex long instructions of the present invention may beadvantageously used in the computation of a covariance matrix. As anexample, consider an antenna array consisting of several elementsarranged in a known geometry. Each element of the array is connected toa receiver that demodulates a signal and produces a complex-valuedoutput. This complex-valued output is sampled periodically to produce adiscrete sequence of complex numbers. The elements from this sequencemay be organized into a vector of a certain length, called a frame, andmay be combined with the vectors produced from the remainder of theantenna elements to form a matrix.

For an antenna array with M elements and K samples per frame, a matrix Uis created.

$U_{M \times K} = \begin{bmatrix}\left\lbrack {{u_{0}(0)}\mspace{20mu}{u_{0}(1)}\mspace{14mu}\ldots\mspace{14mu}{u_{0}\left( {K - 1} \right)}} \right\rbrack \\\left\lbrack {{u_{1}(0)}\mspace{20mu}{u_{1}(1)}\mspace{14mu}\ldots\mspace{14mu}{u_{1}\left( {K - 1} \right)}} \right\rbrack \\\vdots \\{\;\left\lbrack {{u_{M - 1}(0)}\mspace{20mu}{u_{M - 1}(1)}\mspace{14mu}\ldots\mspace{14mu}{u_{M - 1}\left( {K - 1} \right)}} \right\rbrack}\end{bmatrix}$ R_(M × M) = U × U^(H)

In problems such as direction of arrival algorithms, it is necessary tocompute the covariance matrix from such received data. For zero-mean,complex valued data, the covariance matrix, R, is defined to be

where ‘H’ is the hermitian operator, denoting a complex conjugate matrixtranspose.

For example, assuming M=12 and K=128, the elements of R are computed as

${R_{i,j} = {\sum\limits_{k = 0}^{K - 1}{{u_{i}(k)} \times \left( {u_{j}(k)} \right)^{*}}}},$which corresponds to the summation of 128 complex conjugate multipliesfor each of the 144 elements of R. As seen in FIG. 11A, R is a 12×12matrix 1100. R is conjugate-symmetric, so the upper triangular portionof R is the complex conjugate of the lower triangular portion.R_(i,j)=R_(j,i)* for i≠j. As seen in FIG. 11B, this symmetry allows anoptimization such that only 78 elements of R, the lower triangularportion and the main diagonal, need to be computed, as the remainingelements are the conjugated copies of the lower diagonal.

Each element in U is represented as a 16-bit, signed (15 informationbits and 1 sign bit), complex value (16-bit real, 16-bit imaginary).Fixed-point algebra shows that the multiplication of two such valueswill result in a complex number with a 31-bit real and 31-bit imaginarycomponent (30 information bits and 1 sign bit). The accumulation of 12831-bit complex numbers, to avoid saturation (achieving the maximumpossible positive or minimum possible negative value available for thegiven number of bits), requires 39 bits of accuracy in both real andimaginary components (38 information bits and 1 sign bit). Therefore tocompute the covariance matrix for this system, it is necessary toutilize the complex multiply-accumulate function that achieves 31complex bits of accuracy for the multiply, and can accumulate thesevalues to a precision of at least 39 complex signed bits.

The computation of the 78 elements of the covariance matrix 1100 may beadvantageously accomplished with the ManArray 2×2 iVLIW SIMD processor100 shown in FIG. 1. Utilizing the single cycle pipeline multiplycomplex conjugate long with extended precision accumulate (MPYCXJLXA)instruction described above, 128 complex multiplies can be executed inconsecutive cycles. As the iVLIW processor 100 allows 64 bits to beloaded into each PE per cycle, the computation of a single length 128complex conjugate dot product is accomplished in 130 cycles, for a 2cycle MPYCXJLXA. For a single cycle MPYCXJLXA, the computation isperformed in 129 cycles.

FIGS. 11C-11I show the computations performed by the 4 PEs (PE0, PE1,PE2 and PE3) of processor 100 to calculate the 78 elements of thecovariance matrix R 1100. As seen in FIG. 11C, for iteration 1 PE0performs the multiplications for R_(0,0), PE1 performs themultiplications for R_(1,1), PE2 performs the multiplications forR_(2,2), and PE3 performs the multiplications for R_(3,3). As seen inFIG. 11D, for iteration 2 PE0 performs the multiplications for R_(4,4),PE1 performs the multiplications for R_(5,5), PE2 performs themultiplications for R_(6,6), and PE3 performs the multiplications forR_(7,7). As seen in FIG. 11E, for iteration 3 PE0 performs themultiplications for R_(8,8), PE1 performs the multiplications forR_(9,9), PE2 performs the multiplications for R_(10,10), and PE3performs the multiplications for R_(11,11). FIGS. 11F-H show themultiplications for iterations 4-11, 12-15, 16-18 and 19-20,respectively. Thus, the computation of the 78 elements of the covariancematrix from a 12×128 data matrix of 16-bit signed complex numbers occursin 20 (dot product iterations)×130 (cycles per dot product)=2600 cycles,plus a small amount of overhead. The remaining elements of R are simplythe conjugated copies of the lower diagonal. Prior art implementationstypically would consume 79,872 cycles on a single processor with 8cycles per complex operation, 128 complex operations per dot product and78 dot products.

While the present invention has been disclosed in the context of variousaspects of presently preferred embodiments, it will be recognized thatthe invention may be suitably applied to other environments consistentwith the claims which follow.

1. An apparatus for extending the precision of a complex multiplicationwith accumulation, the apparatus comprising: a reduced precision storageunit for storing at least two complex operands, a reduced-precision realvalue, and a reduced-precision imaginary value; an extended-precisionstorage unit for holding an extended-precision real component and anextended-precision imaginary component; multipliers for multiplicationof the two complex operands accessed from the reduced-precision storageunit to produce real and imaginary components of a complex product; afirst integrated product adder and accumulator (IPAA) for addition andsubtraction of real and imaginary components of the complex productcombined with addition of an extended-precision real value producing anaccumulated real result, the extended-precision real value formed by aconcatenation of the extended-precision real component with thereduced-precision real value, and the accumulated real result madeavailable for storing back an updated extended-precision real componentin the extended-precision storage unit and an updated reduced-precisionreal value in the reduced-precision storage unit; and a secondintegrated product adder and accumulator (IPAA) for addition andsubtraction of real and imaginary components of the complex productcombined with addition of an extended-precision imaginary valueproducing an accumulated imaginary result, the extended-precisionimaginary value formed by a concatenation of the extended-precisionimaginary component with the reduced-precision imaginary value, and theaccumulated imaginary result made available for storing back an updatedextended-precision imaginary component in the extended-precision storageunit and an updated reduced-precision imaginary value in thereduced-precision storage unit.
 2. An apparatus according to claim 1wherein the reduced-precision storage unit further comprises: aselectable odd-numbered addressable storage for storing the updatedreduced-precision real value; and a selectable even-numbered addressablestorage for storing the updated reduced-precision imaginary value. 3.The apparatus of claim 2 wherein the extended-precision storage unitfurther comprises: a selectable odd-numbered addressable storageassociated with the selectable odd-numbered addressable storage of thereduced-precision storage unit for storing the updatedextended-precision real component; and a selectable even-numberedaddressable storage associated with the selectable even-numberedaddressable storage of the reduced-precision storage unit for storingthe updated extended-precision imaginary component.
 4. The apparatus ofclaim 2 wherein the selectable odd-numbered addressable storage furthercomprises: a byte from byte position 1 of bytes 0, 1, 2, and 3associated with a selected addressable storage of the reduced-precisionstorage unit being one storage address from every other odd storageaddress beginning at 1 for storing the updated extended-precision realcomponent; and a byte from byte position 3 of bytes 0, 1, 2, and 3associated with a selectable addressable storage of thereduced-precision storage unit being one storage address from everyother odd storage address beginning at 3 for storing the updatedextended-precision real component.
 5. The apparatus of claim 2 whereinthe selectable even-numbered addressable storage further comprises: abyte from byte position 0 of bytes 0, 1, 2, and 3 associated with aselected addressable storage of the reduced-precision storage unit beingone storage address from every other even storage address beginning at 0for storing the updated extended-precision imaginary component; and abyte from byte position 2 of bytes 0, 1, 2, and 3 associated with aselectable addressable storage of the reduced-precision storage unitbeing one storage address from every other even storage addressbeginning at 2 for storing the updated extended-precision imaginarycomponent.
 6. A method for extending the precision of a complexmultiplication with accumulation in a processor, the method comprising:multiplying two complex number operands accessed from a reducedprecision storage unit to produce four real and imaginary components ofa complex product in response to a processor issued multiply complexwith extended precision accumulate instruction; adding two selected realand imaginary components of the complex product to produce a realresult; subtracting two remaining selected real and imaginary componentsof the complex product to produce an imaginary result; adding anextended-precision real value with the real result to produce anaccumulated real result, the extended-precision real value formed by aconcatenation of an extended-precision real component stored in anextended-precision storage unit with a reduced-precision real valuestored in a reduced precision storage unit, and the accumulated realresult made available for storing back an updated extended-precisionreal component in the extended-precision storage unit and an updatedreduced-precision real value in the reduced-precision storage unit; andadding an extended-precision imaginary value with the imaginary resultto produce an accumulated imaginary result, the extended-precisionimaginary value formed by a concatenation of an extended-precisionimaginary component stored in an extended-precision storage unit with areduced-precision imaginary value stored in a reduced precision storageunit, and the accumulated imaginary result made available for storingback an updated extended-precision imaginary component in theextended-precision storage unit and an updated reduced-precisionimaginary value in the reduced-precision storage unit.
 7. The method ofclaim 6 further comprising: receiving a multiply complex long extendedprecision accumulate (MPYCXLXA) instruction; and executing the MPYCXLXAinstruction to extend the precision of the complex multiplication withaccumulation result.
 8. The method of claim 7 wherein the MPYCXLXAinstruction is received in parallel in a plurality of processingelements (PE) for execution in parallel.
 9. The method of claim 7further comprising: storing in an intermediate set of registers the fourreal and imaginary components of a complex product produced at the endof a first pipeline cycle; and storing the accumulated real result andthe accumulated imaginary result in program accessible target registersproduced at the end of a second pipeline cycle, wherein a secondMPYCXLXA instruction is started to execute in the first pipeline cyclewhile a first MPYCXLXA instruction is started to execute in the secondpipeline cycle.
 10. A method for extending the precision of a complexconjugate multiplication with accumulation for the execution of amultiply complex conjugate long extended precision accumulate(MPYCXJLXA) instruction in a processor, the method comprising:multiplying two complex number operands accessed from a reducedprecision storage unit to produce four real and imaginary components ofa complex product in response to a processor issued MPYCXJLXAinstruction; adding two selected real and imaginary components of thefour real and imaginary components of the complex product to produce aconjugate real result; subtracting two remaining selected real andimaginary components of the four real and imaginary components of thecomplex product to produce a conjugate imaginary result; adding anextended-precision real value with the conjugate real result to producean accumulated conjugate real result, the extended-precision real valueformed by a concatenation of an extended-precision real component storedin an extended-precision storage unit with a reduced-precision realvalue stored in a reduced precision storage unit, and the accumulatedconjugate real result made available for storing back an updatedextended-precision real component in the extended-precision storage unitand an updated reduced-precision real value in the reduced-precisionstorage unit; and adding an extended-precision imaginary value with theimaginary result to produce an accumulated conjugate imaginary result,the extended-precision imaginary value formed by a concatenation of anextended-precision imaginary component stored in an extended-precisionstorage unit with a reduced-precision imaginary value stored in areduced precision storage unit, and the accumulated conjugate imaginaryresult made available for storing back an updated extended-precisionimaginary component in the extended-precision storage unit and anupdated reduced-precision imaginary value in the reduced-precisionstorage unit.
 11. The method of claim 10, further comprising: providinga data array U_(M×K) having M elements and K samples, wherein eachelement in U comprises a 16 bit real value and a 16 bit complex value;and executing the MPYCXJLXA instruction M times to calculate a firstelement R of a covariance matrix R_(M×M)=U×U^(H).
 12. The method ofclaim 11 wherein the MPYCXJLXA instruction is pipelineable.
 13. Themethod of claim 11 wherein the first element of R is at least 39 complexsigned bits.
 14. The method of claim 11 wherein the MPYCXJLXAinstruction completes execution in 2 cycles.
 15. The method of claim 11wherein the MPYCXJLXA instruction completes execution in a single cycle.16. The method of claim 11 wherein the step of calculating a firstelement further comprises the steps of: initiating a first execution theMPYCXJLXA instruction in a first cycle; and initiating a secondexecution of a second MPYCXJLXA instruction in a second cycle, thesecond cycle immediately following the first cycle.
 17. The method ofclaim 11 further comprising the step of: calculating a second element ofR utilizing the MPYCXJLXA instruction which executes M times.
 18. Themethod of claim 17 wherein the step of calculating a first elementutilizes a first processing element (PE) of an array of PEs and the stepof calculating a second element utilizes a second PE and both the stepof calculating a first element and the step of calculating a secondelement occur simultaneously.
 19. The method of claim 10 wherein: eachof the two complex number operands are n/2 bits, the reduced-precisionreal value and the reduced-precision imaginary value are each n bits,the extended-precision real component is n/4 bits, and theextended-precision imaginary component is n/4 bits.
 20. The method ofclaim 10 further comprising: executing a multiply complex conjugate long(MPYCXJL) instruction by inserting a zero in place of theextended-precision real value and in place of the extended-precisionimaginary value; storing back the accumulated conjugate real result inthe reduced-precision storage unit without storing back an updatedextended-precision real component in the extended-precision storageunit; and storing back the accumulated conjugate imaginary result in thereduced-precision storage unit without storing back an updatedextended-precision imaginary component in the extended-precision storageunit.